For use environments such as vehicle backup cameras, it may be desirable to enclose an optical device in a housing to protect the optical device from contaminants including fluids, particles, and other unwanted matter. However, the optical device should still be in visual contact with the ambient space outside the housing for many such use environments. The optical devices are often too small to warrant the expense and inconvenience of a transversely-wiping squeegee or other mechanically contacting clearance devices. As a result, an ultrasonic transducer may be provided to longitudinally and/or laterally vibrate a transparent cover portion of the housing along an axis of the lens. The cover vibration occurs at very high frequencies, and acts to break up liquid surface tension, overcome adhesion due to electrostatic and/or Van der Waals forces, and otherwise shake contaminants away from the outer cover surface. However, this ultrasonic vibration can be damaging to various portions of the housing and the enclosed optical device (or components associated therewith), due to unwanted ultrasonic welding effects and/or mechanical wear.